The present invention relates to novel catheters suitable for delivering an electric current to the body, in particular to catheters that have electrodes that can be positioned independently of the main elongate shaft of the catheter. More particularly the invention relates to catheters that include a movable sleeve that incorporates the electrodes. It also relates to a movable sleeve that includes one or more electrodes and to advances in the construction of the electrodes and related components. The invention also relates to methods for positioning electrodes at a treatment site in the body for diagnostic or therapeutic applications.
Catheters that include electrodes that are used for diagnosis, measuring and other medical applications are well known, catheters comprising multiple electrodes, for example, see U.S. Pat. No. 5,109,870 Silny. Whilst catheters comprising electrodes are known in the art, they suffer from a number of disadvantages.
International patent publication No. WO 2006/024825 (Hamdy) discloses a catheter for assisting recovery from dysphagia including a catheter for insertion into the body of a patient via the mouth or nose, a particularly useful application of the devices of the present invention. The electrodes are in the elongate shaft of the catheter such that when the catheter is in a suitable position within the patient's body, the electrodes are in a position to apply electrical pharyngeal stimulation.
The present inventors have, however, found that accurate positioning of the catheter disclosed in Hamdy can be problematic. The catheter is required to fulfil two functions—firstly to safely and effectively deliver nutrition to the patients' stomach via an internal lumen of the elongate shaft of the catheter and secondly to deliver electrical stimulation to a defined region of the oropharynx via electrodes on the outer surface of elongate shaft of the catheter. The incorporation of both functions into the main body of the catheter has advantages, it minimises patient discomfort and is consistent with existing standards of care in that it replaces a conventional nasogastric (NG) feeding tube and can be introduced into the patient in the same way as a conventional NG tube.
The fixed position of the electrodes has, however, been found by the inventors to have some disadvantages. The catheter must be inserted into the patient so that the distal end is correctly positioned in the stomach to meet the requirement to safely
and effectively deliver nutrition. The correct insertion distance can vary considerably dependent on the height of the patient and can routinely be different by 20 cm or more from patient to patient. In contrast, the optimal position for the electrodes in the oropharynx is within a 2-3 cm vertical distance range. Thus, in order to ensure that 5 the electrodes on the elongate shaft of the catheter are correctly positioned there must either be a range of catheter sizes to accommodate the variation in patient height, or the catheter must be designed to be sufficiently long for the tallest anticipated patient and then over inserted into shorter patients in order to bring the electrodes into the correct position. This introduces risks that the distal end of the catheter does not remain in the stomach but continues into the duodenum, becomes entangled in the stomach preventing effective nutrition delivery or easy removal, or re-emerges from the stomach into the lower oesophagus.
The fixed positioning of both electrical stimulation and nutrition functions in the invention of Hamdy et al. also has the disadvantage that, in the event the internal lumen of the catheter becomes blocked with nutritional feed in a way that cannot be resolved, the entire catheter must be replaced.
In addition, it has become apparent that once the treatment with electrical stimulation has been completed it may still be necessary to keep the catheter in place solely for the purposes of enteral nutrition. This is not desirable from a patient comfort or safety management perspective. It would be particularly advantageous for these reasons to be able to remove the electrical stimulation functionality, whilst leaving the nutrition delivery functionality in place.